1. Field of the Invention
This invention relates generally to cartridges for guns and ordnances, and more specifically to cartridges having rapidly increasing sequential ignitions.
2. Description of the Related Art
Most projectiles are conventionally accelerated using chamber-based systems, in which a pressure spike is created in a cartridge. Following that pressure spike, the ability to accelerate a projectile using the full length of a desired barrel is greatly diminished, resulting in an untapped potential of the barrel length for optimized acceleration. The most common approach to solving this problem has been the use of stratified propellants, or blended powders using regular powders intermixed with powder containing chemical retardants to slow the natural burn rate of the powder to extend the burn further down the barrel. Both methods add unnecessary cost and complexity to manufacturing the desired cartridge-based solutions. Most stratified propellant approaches utilize a lacquer or resin that must cure prior to loading the next layer of powder, which is undesirable during commercial manufacturing. Another approach has been the use of spacers, typically consisting of metal, felt, or other similar materials placed between powder layers to deflagrate the natural burn rate. These methods can reduce the case volume and present mass production challenges in the insertion process. Powders with retardants are less efficient, more costly, and are limited in their ability to provide ever-increasing pressure for the full length of a barrel. Duplex loads have also been attempted, whereby a layer of one type of powder is stacked directly above a layer of another type of powder without a barrier. This method, however, has been minimally effective, as a flashover of both powders can occur. The second layer of powder can only burn slightly faster, or the flashover of the two powders can create dangerous pressures and lower velocities. Some prior art solutions are presented below for reference.
U.S. Pat. No. 34,615, A. Shannon in 1862 references perforated diaphragms whereby the number of perforations determines the burn rate between layers.
U.S. Pat. No. 751,519 describes the use of tinfoil or felt diaphragms to slow the burn rate between layers.
U.S. Pat. No. 1,920,075 describes the use of lacquer or salt discs to separate layers as well as igniting from the front and moving rearward.
U.S. Pat. No. 2,072,671 describes cellulose capsules mixed throughout powder intended to delay the second ignition.
U.S. Pat. No. 4,593,622 describes using gas permeable barriers to separate charges.
U.S. Pat. No. 5,031,541 describes the use of a hermetic barrier comprised of polymeric resin and a support disc.
U.S. Pat. No. 5,510,062 describes the uses of a cellulosic thermoplastic deterrent or burn rate modifier.
There exists, therefore, a need for a simpler, more efficient way to manufacture cartridges that can accelerate a projectile to higher velocities with lower pressures and recoil.